xplanet, is a wonderful little program that will render various celestial objects including everyone’s favorite, earth. Thinking of cron, a fun trick might be to make a cronjob which paints a background of the world, and then use that image as the desktop.
A few notes, useful at least for me, the location of NYC is 40.809634,-73.961506 or -latitude 40.809634 -longitude -73.961506.
To fetch the newest cloudmap (checking to see if the server version has been updated)
wget -N http://xplanet.sourceforge.net/clouds/clouds_4096.jpg